Journal of Agricultural Biotechnology and Sustainable Development Vol. 3(10), pp. 198-204, December 2011 Available online at http://www.academicjournals.org/JABSD DOI: 10.5897/JABSD10.030 ©2011 Academic Journals Full Length Research Paper Effects of nitrogen and phosphorus fertilizers and cotyledon removal on establishment and growth of yeheb nut bush ( Cordeauxia edulis Hemsl.) outside its natural habitat Bertukan Mekonnen 1*, Kebede Woldetsadik 1, Tamado Tana 1 and Asha Yahya 2 1Department of Plant Sciences, Haramaya University, P. O. Box: 138, Dire Dawa, Ethiopia. 2Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Sweden. Accepted 13 September, 2011 Yeheb nut bush ( Cordeauxia edulis ) is a multipurpose but endangered shrub native to arid south- Eastern Ethiopia and Central Somalia. Establishment of this species was studied in two sets of experiments during 2005 to 2007. In the first set of experiment, field establishment was conducted at Dire Dawa, Ethiopia, which is located 725 km north west of the natural habitat (Bokh). Nitrogen at 0, 46 and 92 level and phosphorus at 0, 4 and 8 kg ha -1 were applied 84 days after transplanting. Application of 92 N/8 P kg ha -1 increased seedling height by 134%; 46 N/4 P kg ha - 1 increased leaf area by 152% and dry weight of seedlings increased by 309% at 46/8 kg ha -1 NP compared to the unfertilized plants. Nitrogen and phosphorus fertilizers significantly altered soil as well as plant tissue N and P contents. Leaf and root N was significantly highest at 46 and 92 N kg ha -1, respectively while leaf P was maximised at 8P kg ha -1. In the second set, the impact of cotyledon removal was assessed in the greenhouse, Haramaya University by excision of cotyledon at 7 days interval for ten consecutive weeks and leaving the cotyledon with plant as a control. Removing cotyledon at 7, 14 and 35 days after germination (DAG) significantly reduced most of the growth parameters while seedlings with intact cotyledon had the highest dry matter accumulated. Thus, 46 to 92 kg N and 8 kg P ha -1 would help the establishment and growth of C. edulis in the field and seedlings should retain cotyledon during early establishment. However, more rates of N and P as well as methods and frequency of applications deserve further investigation. Key words: Cordeauxia edulis , cotyledon, Ethiopia, nitrogen and phosphorus fertilizers, seedling establishment. INTRODUCTION Yeheb nut bush (Cordeauxia edulis ) is leguminous, multi- 28°C and grows at altitudes of 300 to 1000 m.a.s.l stemmed and evergreen shrub limited to arid south- (Drechsel and Zech, 1988). C. edulis adapted to nutrient eastern Ethiopia near Bokh and central Somalia impoverished soil (Seegeler, 1983; Drechsel and Zech, (Seegeler, 1983; Booth and Wickens, 1988; Zimsky, 1988) and frost free areas. It is the only species within 1990). It typically experiences erratic rainfall as low as the genus Cordeauxia . 100 to 200 mm year -1, average annual temperature of The seed of C. edulis is nutritious and tasty with a chestnut flavour. They contain 37% starch, 24% low molecular weight sugar, 13% proteins, 11% fats and various mineral salts (Gutale and Ahmed, 1984). The nut *Corresponding author. E-mail: is the staple food for the local people which is liked to the [email protected]. Tel: +251 25 553 03 19/20. common diet of rice and dates (Kazmi, 1979). The nut Fax +251-25-553 03 25 /31. has also medicinal value and economic importance at Mekonnen et al. 199 local market and even across the continent (Booth and could be brought by herbivores, insect pests and Wickens, 1988). In general, C. edulis has multiple uses: diseases. Large numbers of seedlings of C. edulis are as fodder, firewood, house construction, bee food supply, destroyed by goats and camels during browsing mulch, soil conservation, live fence, dyes etc. (Azene et (Johnson, 1996) and re-growth of grazed seedlings may al., 1993). Moreover, it is a very drought tolerant and be dependent on nutrient reserve. Milberg and Lamont often represents the last existing perennial. The palatable (1997) reported that the effect of cotyledon removal was leaves are dry season browse for animals (Drechsel and least in the smallest–seeded Eucalyptus loxophleba Zech, 1988). Further, C. edulis has the potential to be a Benth and greatest in the largest-seeded, Haeka reliable source of protein and valuable food crop in hot psilorrhyncha R. M. Barker. Taylor et al. (2006) animal and dry regions (Zimisky, 1990). It could be particularly browse protection is considered indispensable for important for places where rainfall is scares for growing successful seedling establishment of Quercus . more conventional crops (Vietmeyer, 1985). It is a prerequisite to know the stage at which cotyledon However, C. edulis is threatened by extinction in its loss or damage might bring significant impact on seedling natural habitat because of wars, recurrent drought, over- establishment of C. edulis to enable take measure at that harvesting and heavy grazing (Miége and Miége, 1978; specific time or phase. Therefore, the aim of this study Zimsky, 1990). Thus, introduction of this multipurpose was to determine the influence of NP fertilizers on C. shrub to arid and semiarid tropics is greatly in need to edulis growth and to assess the importance of cotyledon minimize the threatening of this species. to C. edulis establishment. One of the conditions which influence establishment and growth of plants is soil fertility. Nitrogen and phosphorus are among the major essential nutrient MATERIALS AND METHODS elements for improving plant growth and development. Experimental locations and seed material Olaniyi (2008) reported that various levels of individual and combined N and P fertilizers significantly improved The field experiment (Experiment 1) was conducted at Dire Dawa, growth and seed yield of Citrullus lanatus . Mhango et al. Ethiopia (09° 31 'N, 41° 51' E), about 500 km east of the capital, (2008) showed the importance of NPK fertilizer in Addis Ababa, and 725 km west of the natural habitat at an altitude improving seedling growth of Uapaca kirkiana . Similarly, of 1160 m.a.s.l. The experimental site is characterized as semi-arid tropical climate with average annual rainfall of about 644 mm (NMA, Picea glauca growth and nutrient uptake increased by 2006). The rainfall has a bi-modal distribution pattern with small application of N fertilizer during its seedling stage rains from March to May and long and moderate rains from June to (Mcalister and Timmer, 1998). C. edulis native area is September. The experimental soil is alluvial with a sandy clay loam characterized by red coloured sandy soil which is to sandy loam texture and a pH of 8.6. The physic-chemical extremely low in nitrogen (Drechsel and Zech, 1988; characteristics of the experimental and the native soils are shown in Zimisky, 1990). According to Sassaki and Felipe (1998) Table 1. Plots were selected for the field experiment from a large piece of Dalbergia miscolobium Benth which is occurring on a grazing land covered with grass during the previous nine years and very poor soil responded positively to the addition of fertilized with animal manure for four years preceding the study. mineral nutrients when the plants were grown in pots. In The experimental plots were prepared by digging the soil to one another study, seedling growth of Acacia auriculiformis meter depth preceding planning. was enhanced significantly with the application of Experiment 2 was conducted in a greenhouse at Haramaya phosphorus fertilizers (Uddin et al., 2007). There might University, Ethiopia (9° 26' N, 42° 3' E). The fruits of C. edulis were collected from natural vegetation in be a possibility of increasing establishment of C. edulis Gambarey village near Bokh town (7°22`N, 46° 35`E), Warder Zone through supplying fertilizer. of Eastern Ethiopia, 725 km south east of the study site, Dire Dawa. Rate of fertilizers is considered as one of the factors The fruits were gently dried in shade after harvest; the pericarps that affect plants growth. According to Hossain and were removed and the seeds were kept in cotton-cloth bag at room Hamid (2007), growth and yield of groundnut exhibited temperature until used for the experiments. improved growth and yield with increased rate of N and P application. Jeppsson (2000) reported that vegetative Experiment 1: Nitrogen and phosphorus fertilizer supply growth and yield of Aronia melanocarpa increased with a combined application of NPK fertilizer in different rates. The treatments consisted of 3 levels of N (0, 46, 92 kg ha -1) and 3 -1 The other factor which affects establishment of plants is levels of P (0, 4, 8 kg ha ) using urea (46% N) and triple super phosphate (20% P) as a source of N and P, respectively. Nine the seed nutrient reserve (cotyledon). Large seeded -1 treatment combinations (0N0P, 0N4P, 0N8P, 46N0P, 46N4P, species, including C. edulis (1.8 to 2.4 g dwt seed ; 46N8P, 92N0P, 92N4P and 92N8P kgha -1) were laid out in a Andersson et al., 2007) rely heavily on nutrient support randomised complete block design in three replications. from the cotyledon than from the soil (Milberg and Seedling were raised from ca 1400 seeds which were peeled Lamont, 1997; Vaughton and Ramsey, 2001) to survive fourteen days after harvest and sown on 20 June 2005 in a under unfavourable conditions and hazards during the greenhouse. One seed was sown per polyethylene bag in partially- buried position after the bag was filled with sieved river sand and establishment phase (Frost and Rydin, 1997; Kidson and well watered. The bags were open-ended on both sides and had a Westoby, 2000).